I'm puzzled by the answer that Intel have given. Why is it that it is not compatible? Just over at Arctic Cooling; their products (for example the Alpine 11 Pro Rev. 2 can be used for both the E8400 and the E6850). Please explain in detail as to why the parts are not compatible. Thanks in advance.

Comparing the Intel® Core™ 2 Duo Processor E8400 and the Intel® Core™ 2 Duo Processor E6850, they are designed with a different lithography; the Intel® Core™ 2 Duo E8400 is a 45nm processor while the Intel® Core™ 2 Duo E6850 is a 65nm. Due to this, the cooling solution between them differs.